The disclosure relates generally to turbomachines, and more particularly, to systems and methods for monitoring health of components, such as stationary blades or stator vanes.
Turbomachines and other complex machines include a large number of mechanical components, including both static and moving components. These components may be subject to stress and wear, particularly in applications and environments that include motion, pressure, and heat. An example of such components are the stator vanes of a gas turbine.
A gas turbine may include an axial compressor at the front, one or more combustors around the middle, and a turbine at the rear. Typically, an axial compressor has a series of stages with each stage comprising a row of rotor blades or airfoils followed by a row of stationary blades or static airfoils, referred to as stator vanes. Accordingly, each stage generally comprises a pair of rotor blades and stator vanes. Typically, the rotor blades increase the kinetic energy of a fluid that enters the axial compressor through an inlet and the stator vanes convert the increased kinetic energy of the fluid into static pressure through diffusion. Accordingly, both sets of airfoils play a vital role in increasing the pressure of the fluid.
Axial compressors incorporating stator vanes are used in a variety of applications, including land based gas turbines, jet engines, high speed ship engines, small scale power stations, or the like. Similar axial compressors may be used in other applications, such as large volume air separation plants, blast furnace air, fluid cracking air, propane dehydrogenation, or other industrial applications.
Moisture, high temperatures, vibration, particulates, chemicals, and other factors in the environment lead to corrosion of various components within a gas turbine or other harsh operating conditions. In combination with operational fatigue in the components, this leads to stress-corrosion cracking. Stress-corrosion cracking can be seen most dramatically in cases of abnormal resonances or impact of foreign objects. Stress and fatigue over time leads to defects and cracks that can then propagate or grow to the point where they present a risk of device failure, such as the liberation of an airfoil and the resulting destruction a large free object wreaks within the device.
Conventional systems and methods exist to monitor the performance and operation of compressors and their airfoils. For example, vibration sensors may be used to monitor vibrations from machines and their components during operations. A change in the frequency or magnitude of existing vibrations may indicate excessive wear and/or crack formation. However, vibration sensors may only detect cracks and other anomalies that are large enough to cause imbalance and vibration in the machine. As a result, vibration sensors may not detect small cracks that do not result in a detectable vibration in a components, such as a stator vane.
Systems using sensing devices configured to detect acoustic emission (AE) signals have also been proposed for machines and components, such as compressors and stator vanes. The AE signals propagate through the machine components and are received by AE sensors. The AE signals are then processed to determine whether signals of interest are present and, if so, used to monitor and validate the health of the components. Improved techniques for identifying and analyzing specific AE signal features corresponding to component health are desirable.